2. Field of Use
The field of use for the hypodermic injection device described herein is for injecting fluids into or withdrawing fluids from living or non-living organisms or inanimate objects, all of the foregoing generically referred to a thing 68 or sometimes as a body. With respect to living or nonliving organisms, the hypodermic injection device is generally used for injecting medicine into the body or withdrawing fluids from the body. Frequently, injections are made into subcutaneous tissues and fluids are withdrawn from cavities within the body. Although, the major use of the hypodermic injection device will most likely be in connection with the treatment of humans and human cadavers; application of the device will also be found in connection with other animals and their cadavers and also plants. Uses of the device will also be found in connection with inanimate articles and materials. For illustration purposes only, the description of this invention will center around use of the hypodermic injection device in connection with the treatment of humans.
3. Description of the Related Art
There are many hypodermic injection devices on the market today. These devices are ubiquitous in the medical arts. They are used in both the clinical and surgical settings. Hypodermic injection devices suffer from several shortcomings. The extended needle poses a hazard to both the medical caregiver and the patient from accidental needle pricks. The devices do not have a nearly fail-safe method of self-destruction after use; thereby allowing possible reuse and the concomitant transmission of disease. Disposal of the injection device also poses some risk of accidental needle pricks due to the extension of the islet or needle portion of the used injection device. The exposed islet also necessitates special disposal containers for sharp contaminated articles. Furthermore, hypodermic injection devices rarely feature a safety mechanism for locking the injection device so that fluid may not be accidentally expelled, and when they do the safety mechanism is not easy and fast to use during surgery, for example.
Today with the proliferation of many blood borne contagious diseases such as AIDS and Ebola, the frequent use of hypodermic injection devices poses a serious threat of infection. This is especially true in the surgical setting. Surgery is usually a team effort. It often requires the use of multiple hypodermic injections or the withdrawal of fluids from a patient. It is not uncommon for surgery to take place under emergency conditions. All of these factors combine to set the stage for accidental needle pricks to surgical team members with the attendant uncertainty of possible infection. Many times, it is not possible to determine for an extended period of time whether the caregiver has been infected as a result of a needle prick. The result can be actual infection with a lethal blood borne pathogen or a prolonged period of anguish and worry only to discover that the caregiver is not infected. Besides the anguish, the care giver is not infrequently side-lined from performing surgery for fear that he/she may in fact be infected and may transmit the disease to a patient or other member of the surgical team. While the surgical arena presents the highest level of accidental needle pricks, other more pedestrian areas of medical practice also present significant risks, such as in the everyday clinical practice of medicine.
It has long been recognized that the needle prick risk factor needs to be controlled. Training and care while using hypodermic needles is emphasized. But, this, in of itself, is not enough, considering the high probability of a needle prick and the disastrous level of damage to health that it can inflict upon both the patient and caregiver.
It is common practice in the health care industry to use a hypodermic injection device only once and then to dispose of it in a safe manner. However, it is also well known that intravenous drug users often reuse hypodermic injection devices and share them with other users. This, of course, is one of the major reasons for the high prevalence of AIDS and other blood borne infections among such drug users. It is also a major cause of infection of the sexual partners of intravenous drug users. The hypodermic injection device of the present invention is designed to be a single use device. Any attempt to refill the injection device results in retraction of the needle into the fluid reservoir in the barrel of the injection device. The nozzle end of the needle then drops into the reservoir of the injection device making it virtually impossible to extend the needle through the guide-way and outside of the barrel. With the needle tilted into the distal end of the reservoir, it is simultaneously disabled from further use and is safely disposed of, thereby avoiding transmission of blood borne infections by needle sharing and accidental needle sticks. Furthermore, in both the clinic and hospital settings, the disposal of the injection device is much safer and may require a less costly sharps disposal method or device than currently required.
The present invention features a normally retracted needle. This alone reduces risk of accidental needle pricks, since the needle is not exposed so it can injure anyone until it is actually ready to be filled with the injected fluid or to be used for withdrawing fluids.
The present invention also features a locking mechanism that does not allow the needle to be accidentally extended beyond the barrel of the injection device. Extension of the needle requires the user to deliberately depress the tab-like lock, which is integrally molded into the piston. Depression of the lock into the lock depression space in the piston allows the lock to clear the inside diameter of the barrel, allowing the piston to travel in axial alignment into the barrel and thereby extend the needle beyond the distal end of the luer sleeve.
The hypodermic injection device is also amenable to cost-effective manufacture by injection molding. Its novel structure is uncomplicated. And, its method of use is straightforward. One of the components of an embodiment of the injection device is a barrel with an open end, barrel grip, a luer sleeve at the distal end of the barrel in alignment with the central axis of the barrel, an end cap and a septum in the distal end of the luer sleeve, and a guide-way through the luer sleeve in alignment with the central axis. Another component of this embodiment is a piston in alignment with the central axis engaged for axial sliding movement within the inner wall of the barrel. The piston also comprises a lock attached to the piston by a tab for depression into a depression space of a depth to allow the lock to be flush with the diameter of the piston so the piston may be extended into the barrel and the lock may return to a normal raised position upon release of depression pressure to allow the piston to be locked from further axial extension into the barrel. The distal end of the piston has a faceplate with a hook at its periphery for hooking a support plate when the piston is turned within the barrel. The faceplate also has a convex location boss on its distal face for engagement with a concave location boss on a proximal face of the support plate and for disengagement with the concave location boss when the piston is turned within the barrel to hook the support plate. The support plate supports a needle on the central axis, the bore of the needle in communication with an inlet and an undercut for engagement with the hook when the piston is turned within the barrel. The distal end of the needle is supported in the guide-way, the needle having a length such that when the piston is retracted out of the barrel beyond a locked position with respect to the barrel, the needle retracts from the guide-way so that the distal end of the needle is contained within the reservoir. The reservoir is located in the distal end of the barrel when the piston is in the locked position in the barrel. The length of the reservoir is directly related to the longitudinal distance of the location of the lock on the piston from the faceplate.
The above described embodiment of the hypodermic injection device is used in the following manner: (a) with the piston of the injection device in a first position wherein the piston is locked into longitudinally position with respect to the barrel and the distal end of the needle is supported in the needle guide-way, the lock is depressed and then the piston is slid in a distal direction into the barrel to the distal end of the barrel, so that the needle is extended beyond the distal end of the end cap; (b) the needle is extended into a fluid to be injected; (c) the piston is retracted in the proximal direction until the lock engages the proximal end of the barrel, so that the fluid is drawn into the reservoir; (d) the needle is inserted into the thing to be injected; (e) the lock is depressed and then the piston is slid in a distal direction into the barrel to the distal end of the barrel, so that the fluid in the reservoir is injected into the thing to be injected; (f) the piston is turned in the barrel to engage the piston hook with the support plate undercut; and (g) the piston is retracted from the barrel in a proximal direction to a point where the lock is beyond the barrel open end, so that the distal end of the needle is within the reservoir.